When cold the car is fine.. During the warming up period and once warm, the engine hunts and the revs fluctuate by upto 300rpm..
Also, when attempting to accelerate, the engine seems to hesitate and "bogs down" prior to accelerating.
I initially thought this was a gearbox problem but the fluid has been changed together with numerous parts being replaced but the problem persists.
I have no warning lights on and the diagnostic check shows no defects.